1. Field of the Invention
The present invention relates to a device for visually indicating house numbers during both daylight hours and at night. More specifically, this invention relates to such a device which provides an easy modification for different numbers, and is battery operated but causing a low power drain.
2. Description Relative to the Prior Art
Illuminated house numbering devices are well known, and there is much prior art describing such systems. Typical of these is U.S. Pat. No. 5,007,190, which provides a programmable system which is solar powered, thus allowing the device to be installed without connection to the internal wiring system of the house. The solar cells of this prior art device are used to charge an internal battery during the day, and the battery powers the device at night.
Devices such as the one described above suffer from a common shortcoming however: complexity, resulting in high purchase price, and high maintenance and replacement cost.
Furthermore, many of these devices do not provide a numbering visible during the day, since the typical illuminated characters chosen do not provide a display which is easily discernable during daylight hours.
In U.S. Pat. No. 5,522,540, issued Jun. 4, 1996, to Robert L., Surman, titled xe2x80x9cSolar Powered Illuminated Address Number Device and Mailbox Structurexe2x80x9d, the illumination feature is made part of a mailbox in the teaching and in the independent claims. Also the internal battery is powered by solar energy. This invention has the disadvantage of using solar energy to power the battery and the disadvantage of increased cost. Also it is associated with a mailbox and not necessarily useful in other location such as inside buildings.
The device described herein solves these problems by providing a simple, low-cost and low power consuming system which is visible both during the day and at night. The electronics are simple, and the power drain is quite low. The recharging of the battery(s), when necessary, is done off line, further reducing the cost and complexity of the device. Alternatively, the battery(s) may be simply replaced when discharged.
Our solution employs the use of Light Emitting Diodes, (LEDs) which are very efficient in converting electrical energy into light. Also we use a low duty cycle for the current flow through the LEDs to conserve average energy. Further improved energy utilization is achieved by operating the LEDs in series and by powering then from an efficient blocking oscillator.
Furthermore, our invention extends the life of the internal batteries by using an energy conserving technique of powering the illuminating LEDs with low duty cycle pulses so that the average current and energy drawn from the battery is considerably reduced. The pulses are at a high enough frequency (above the critical flicker fusion frequency) so that the viewed numbers and/or letters appear constant due to the persistence of vision. Included are a number of optional features that make the device more versatile without significantly increasing costs or complexity.
Our invention permits display of the numbers and or messages and with high contrast in daylight.
The advantages of the present device include the simplicity of the power supply which uses standard flashlight batteries, the use of low cost electronics to extend battery life, the ability to easily change address numbers and to use different fonts, and flexibility allowing the display of changeable alphabetic messages such as but not limited to street names, or occupant names.
It is an object of the current invention to provide a simple, low-cost illuminated multi-digit house sign in which the numbers contained therein are visible both day and night. It is a specific object of the invention to provide such a sign with a modular design, and providing long battery life.
In accordance with one aspect of the present invention, an illuminated sign includes a power source, an illuminatable panel powered by the power source, and one or more opaque stencils each containing cutouts of a character through which the illuminatable panel is visible. Each of the stencils is disposed near the face of the illuminatable panel, so that the sign""s appearance is one of illuminated characters corresponding to the stencils when the sign is lighted.
In accordance with a second aspect of the invention, the invention includes switching means to switch power from the power source to the illuminatable panel on and off
In accordance with a third aspect of the invention, each stencil also has a background with a background color, and a margin, with a margin color, the margin configured around the cutout. The margin color is different from, and contrasting with, the background color. As a result, the identity of the character is visible even when the illuminatable panel is not illuminated.
In accordance with a fourth aspect of the invention, the power source is a battery.
In accordance with a fifth aspect of the invention, the sign includes a dusk detector and a timer which is activated when the dusk detector detects the onset of dusk and remains activated for an illumination period. As a result, power is switched off from the illuminatable panel except during the illumination period.
In accordance with a sixth aspect of the invention, the sign has a body, and the stencils are retained in the body by slides formed in the body.
In accordance with a seventh aspect of the invention, the illuminatable panel is a florescent illuminatable panel.
In accordance with an eighth aspect of the invention, the illuminatable panel is made up of a substantially equally spaced array of LEDs; a diffuser disposed in front of the illuminatable panel, and one or more opaque stencils each containing cutouts of a character through which the illuminatable panel is visible, each such stencil disposed in proximity to the diffuser.
In accordance with a ninth aspect of the invention, the LEDs are switched on and off at a pulse rate, and after each time the LEDs are switched on they remain on for an on period. Switching means are incorporated to vary the pulse rate, and to vary the duration of the on period.
In accordance with a tenth aspect of the invention, constant current electronic means to are used to illuminate the LEDs.
In accordance with an eleventh aspect of the invention, the diffuser has a whitish color, so that the cutouts in the stencils are easily visible during daylight hours, when the illuminatable panel is not illuminated.
In accordance with a twelfth aspect of the invention, the stencils have a front side and a back side, the front side being dark in color, and the back side having a reflective surface, so that the light from the reflective surface reflects off the diffuser, further illuminating the diffuser.